<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>09-边框_03-形状</title>
    <style>
        body {
            background-color: #ddd;
        }

        div {
            width: 100px;
            height: 50px;
            background-color: #fff;
            border-bottom: 50px solid #000;
            border-radius: 50%;
        }
    </style>
</head>
<body>

<div></div>

</body>
</html>